Process for preparation of high-purity organic compounds

ABSTRACT

There is provided a method for obtaining a target organic compound such as an alkyladamantyl ester efficiently by purifying a crude organic compound which contains, as impurities, sublimable materials which start to sublime at temperatures lower than a boiling point of the target organic compound by use of such a simple method as distillation during its production process, without being adversely affected by adherence of the sublimable materials.  
     The distillation is carried out in the presence of a compound having a boiling point which is lower than a boiling point of the target organic compound, e.g., a carbonyl-group-containing compound. For example, 2-methyl-2-adamantyl methacrylate (boiling point: 92° C./0.3 mmHg) containing sublimable impurities such as adamantane (sublimation starting temperature: room temperature or lower) is distilled in the presence of 1,3-dimethyl-2-imidazolidinone (boiling point: 225° C.).

TECHNICAL FIELD

[0001] The present invention relates to a method for producing a highpurity organic compound. More specifically, it relates to a method forproducing a high purity organic compound by distilling and purifying acrude organic compound containing sublimable materials as impuritiesefficiently.

BACKGROUND ART

[0002] Heretofore, when a high boiling compound containing sublimablematerials as impurities is distilled and purified, there exist apossibility that the sublimable materials block a pipe by subliming anda problem that solid sublimable materials adhered to the pipe dissolvesin a high boiling compound to be distilled out, thereby inhibiting anincrease in purity of the high boiling compound. Thus, it has beendifficult to distill and purify a high boiling compound containingsublimable materials as impurities.

[0003] Meanwhile, demand for products of higher purity has beenincreasing every year. In particular, a reduction in metal components ofa product used in a semiconductor production process is stronglydemanded. As a purification method which can remove such metalcomponents efficiently, purification by distillation is suitable.

[0004] In recent years, it has been reported thatalkyladamantyl(meth)acrylate polymers have high dry etching resistancein a semiconductor production process (refer to JP-A 5-265212), and apossibility of their use as a resist material for a semiconductor hasbeen receiving attention. In the case of thesealkyladamantyl(meth)acrylates as well, those having reduced metalcomponents and high purity are desired for use as a resist material fora semiconductor.

[0005] It is known that the alkyladamantyl(meth)acrylate can begenerally produced by obtaining adamantanone first and thenalkyladamantanol from adamantane as a raw material and then reacting thealkyladamantanol with (meth)acrylic acid, (meth)acrylate, (meth)acrylicanhydride or a (meth)acrylic acid halide. However, since thealkyladamantyl(meth)acrylate which is a target compound is a highboiling compound and adamantane, adamantanone and alkyladamantanolremaining as an unreacted raw material and reaction byproducts aresublimable materials having a sublimation starting temperature(sublimation point) lower than a boiling point of the target compound,it has been difficult to purify the target compound efficiently bydistillation.

[0006] It is an object of the present invention to provide a method forproducing a target compound of high purity by applying an efficientpurification method to a crude organic compound containing sublimablematerials as impurities for which an efficient distillation/purificationmethod has not been known.

[0007] The present inventor has made intensive studies to solve theabove problem. As a result, he has found that a target organic compoundcan be efficiently purified by distilling a crude organic compound inthe presence of a compound having a boiling point lower than that of thetarget organic compound. The present invention has been completed by thefinding.

DISCLOSURE OF THE INVENTION

[0008] To be more specific, the present invention is a method forproducing a high purity organic compound by distilling a crude organiccompound containing, as impurities, sublimable materials which sublimeat temperatures lower than a boiling point of the target organiccompound. It comprises the steps of distilling out a compound having aboiling point lower than that of the organic compound by carrying outthe distillation in the presence of the compound having a boiling pointlower than that of the organic compound so as to cause the compound torinse out sublimable materials sublimed and adhered to the inside of adistillation device or prevent sublimable materials from adhering to theinside of the distillation device and then distilling out and recoveringthe organic compound.

[0009] In the method of the present invention, a crude organic compound(hereinafter also referred to as “compound to be purified”) containingsublimable materials (hereinafter also referred to as “low-temperaturesublimable materials”) which sublime at temperatures lower than aboiling point of a target organic compound is distilled. The compound tobe purified is not particularly limited as long as it is a crude organiccompound containing low-temperature sublimable materials. Illustrativeexamples of the compound to be purified include (i) a reaction solutioncontaining an unreacted raw material which is obtained by synthesizing atarget organic compound through a chemical reaction using a sublimablematerial which sublimes at temperatures lower than a boiling point ofthe organic compound as a raw material, (ii) a crude product obtainedfrom the reaction solution and containing the raw material as animpurity, (iii) a reaction solution containing sublimable materialswhich are produced as byproducts when the organic compound issynthesized through the chemical reaction and sublime at temperatureslower than the boiling point of the organic compound and (iv) a crudeproduct obtained from the reaction solution and containing thebyproducts as impurities.

[0010] An example of an organic compound which inevitably containssublimable synthesis raw material and reaction byproducts in a synthesisreaction of the organic compound as described above is an alkyladamantylester. In a synthesis reaction of the alkyladamantyl ester, a synthesisraw material and byproducts in the synthesis reaction such asadamantane, adamantanone and alkyladamantanol which are sublimablematerials are inevitably mixed into the product. The crude organiccompound obtained in such a synthesis reaction is suitable as an objectto be distilled in the present invention.

[0011] The above alkyladamantyl ester is preferably a high boilingcompound which has a boiling point at normal pressure of not lower than100° C. or a boiling point under a reduced pressure of 1 mmHg of notlower than 40° C. Further, the method of the present invention isparticularly suitable for a case where a difference between a boilingpoint of such an organic compound and sublimation starting temperaturesof low-temperature sublimable materials is at least 10° C., particularly20 to 100° C.

[0012] For example, an alkyladamantyl ester such asalkyladamantyl(meth)acrylate is produced by obtaining adamantanone firstand then alkyladamantanol from adamantane as a raw material and thenreacting the alkyladamantanol with a (meth)acrylic acid halide. In thiscase, obtained reaction solutions or crude products obtained from thereaction solutions generally contain, as impurities, adamantane,adamantanone and alkyladamantanol which are an unreacted raw materialand reaction byproducts. Although depending on a degree of vacuum at thetime of distillation, these impurities are generally low-temperaturesublimable materials whose sublimation starting temperatures are lowerthan a boiling point of an alkyladamantyl ester which is a targetcompound by 100 to 10° C. As a method of purifying the target compoundfrom such reaction solutions by distillation, the method of the presentinvention can be particularly suitably used.

[0013] An alkyladamantyl ester produced by the above method isrepresented by the following formula (1):

[0014] (wherein R³ is a hydrogen atom or an alkyl group having 1 to 6carbon atoms, and R⁴ is a hydrogen atom or a methyl group).

[0015] In the above formula (1), R³ is a hydrogen atom or an alkyl grouphaving 1 to 6 carbon atoms, and R⁴ is a hydrogen atom or a methyl group.Specific examples of the alkyl group having 1 to 6 carbon atoms andrepresented by R³ include linear alkyl groups such as a methyl group, anethyl group, a propyl group, a butyl group and a hexyl group; andbranched alkyl groups such as an isopropyl group, a tertiary butyl groupand a neopentyl group. Particularly, among alkyladamantyl estersrepresented by the above formula (1), those represented by the formula(1) wherein R³ is a methyl group, an ethyl group or a butyl group and R⁴is hydrogen or a methyl group are suitable because they are useful asraw materials for resists for semiconductors and particularly because ahigh degree of purification is important.

[0016] In the present invention, the compound to be purified may alsocontain a material (hereinafter referred to as “third material”) otherthan the target organic compound and the low-temperature sublimablematerials, such as a material without sublimability or a material withsublimability which has a sublimation starting temperature higher thanthe boiling point of the target organic compound. Generally, a compoundwhich can be the third material is a raw material, byproduct or solventused at the time of synthesis of the target organic compound.

[0017] Further, although composition of the compound to be purified isnot particularly limited, the composition is suitably such that thecontent of the target organic compound is 50 to 99 wt %, particularly 70to 99 wt %, based on a total weight of the target organic compound andthe low-temperature sublimable materials, from the viewpoint ofdistillation efficiency or the like. Further, when the third material iscontained, the content of the third material is suitably not higher than50 parts by weight, particularly not higher than 30 parts by weight,when the above total weight is 100 parts by weight.

[0018] In the present invention, distillation of the compound to bepurified is carried out in the presence of a compound (hereinafter alsoreferred to as “distillation assistant”) having a boiling point lowerthan that of the target organic compound so as to purify the targetorganic compound.

[0019] The low-temperature sublimable materials sublime in an earlystage of the distillation and solidify and adhere to the inside ofdistillation devices. The distillation assistant is distilled outconcurrently with, right before or right after sublimation of thelow-temperature sublimable materials according to its boiling point andexhibits an effect of washing out the low-temperature sublimablematerials adhered to the inside of the distillation devices orinhibiting adherence of the low-temperature sublimable materials to theinside of the distillation devices. Therefore, by recovering adistilled-out target organic compound after the low-temperaturesublimable materials are discharged by the distillation assistant, thetarget organic compound to be produced in the present invention can berecovered at a high purity.

[0020] The distillation assistant may be any compound having a boilingpoint which is lower than that of the target organic compound. Theboiling point of the distillation assistant may be higher than and equalto or lower than the sublimation starting temperatures of thelow-temperature sublimable materials. When the boiling point of thedistillation assistant is higher than or equal to the sublimationstarting temperatures of the low-temperature sublimable materials, thedistillation assistant is distilled out concurrently with or aftersublimation of the low-temperature sublimable materials so as to washout the low-temperature sublimable materials adhered to the inside ofthe distillation devices. Even if the boiling point of the distillationassistant is lower than the sublimation starting temperatures of thelow-temperature sublimable materials, the distillation assistant isdistilled out before the sublimation of the low-temperature sublimablematerials so as to prevent the low-temperature sublimable materials fromadhering to the inside of the distillation devices. As a result, thetarget compound can be distilled at a high purity.

[0021] The distillation assistant is preferably one capable ofdissolving the low-temperature sublimable materials in order to recovera high purity organic solvent at a high yield.

[0022] When a distillation assistant which is easily separated from thetarget organic compound is used, the distillation assistant can beremoved easily even if the organic compound is distilled out asdistillation proceeds and mixed with the distillation assistant, so thatthe organic compound can be obtained at a high purity. For example, if awater-soluble distillation assistant is used when the organic compoundis water-insoluble, the organic compound can be obtained easily bywashing a distillate with water. Further, if a water-insolubledistillation assistant is used when the organic compound is easilysoluble in water, an acid solution or an alkali solution, the organiccompound can be obtained easily by dissolving a distillate in water, anacid solution or an alkali solution, removing the distillation assistantby a liquid separating operation or the like, performing aneutralization operation as required, and removing water. In addition,when the organic compound is insoluble in water and stable in acid oralkali, an acid or alkali distillation assistant can be used. In thiscase, the organic compound can be obtained easily by washing adistillate with an alkali or acid solution.

[0023] An appropriate distillation assistant is determined according totypes of the organic compound and low-temperature sublimable materialscontained in the compound to be purified. However, a compound containinga carbonyl group can inhibit adherence of the low-temperature sublimablematerials to the inside of the distillation devices efficiently andmakes it possible to obtain the target organic compound at a high purityeven if the content of the organic compound in the compound to bepurified is low.

[0024] Specific examples of distillation assistants which can besuitably used in the present invention include ethers such asn-butylphenyl ether and dihexyl ether; polyalkylene glycols such asdiethylene glycol, triethylene glycol, tetraethylene glycol anddipropylene glycol; sulfoxides and sulfolanes such as dimethyl sulfoxideand sulfolane; phosphoric amides such as hexamethylphosphoric triamide;non-cyclic or cyclic ketones such as benzyl isopropyl ketone, isopropylphenyl ketone, heptanophenon and methylcyclohexanone; aldehydes such asdecanal and benzaldehyde; esters such as diethylene glycol diacetate andphenyl acetate; non-cyclic amides such as dimethylformamide,dipropylformamide, N-benzylacetamide, acetanilide, 1-formylpiperidine,1-acetylpiperidine, N-formylmorpholine and N,N-diethylacetamide; cyclicamides such as ε-caprolactam, 2-pyrrolidinone, N-methylpyrrolidinone,1-methyl-2-pyrrolidone, 1-methyl-2-piperidone, 2-piperidone,2-pyrrolidone and N-methyl-4-piperidone; non-cyclic ureas such astetraethylurea, 1, 3-diethylurea and 1,1-diethylurea; cyclic ureas suchas 1,3-dimethyl-2-imidazolidinone,1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone, ethyleneurea andtetrahydro-2-pyrimidinone; imides such as phthalimide and succinimide;acid anhydrides such as cyclohexanedicarboxylic anhydride; urethanessuch as methyl carbamate; and lactides. These distillation assistantsmay be used alone or in combination of two or more.

[0025] Of these distillation assistants, cyclic ureas or cyclic amidesrepresented by the following formula (2):

[0026] (wherein R¹ is a hydrogen atom or an alkyl group having 1 to 6carbon atoms, A is —CH₂— or >N—R² (wherein R² is a hydrogen atom or analkyl group having 1 to 6 carbon atoms), and n is an integer of 1 to 6)are particularly preferable since they exhibit particularly goodsolubility to the low-temperature sublimable materials contained in thecrude organic compound which is the compound to be purified and thetarget organic compound can therefore be obtained at a high purity andhigh yield.

[0027] In the above formula (1), R¹ and R² are independently a hydrogenatom or an alkyl group having 1 to 6 carbon atoms. Illustrative examplesof the alkyl group include linear alkyl groups such as a methyl group,an ethyl group, a propyl group, a butyl group and a hexyl group; andbranched alkyl groups such as an isopropyl group, a tertiary butyl groupand a neopentyl group.

[0028] Illustrative examples of particularly preferred distillationassistants include cyclic amides such as E-caprolactam, 2-pyrrolidinone,N-methylpyrrolidinone, 1-methyl-2-pyrrolidone, 1-methyl-2-piperidone,2-piperidone, 2-pyrrolidone and N-methyl-4-piperidone; and cyclic ureassuch as 1,3-dimethyl-2-imidazolidinone,1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone, ethyleneurea andtetrahydro-2-pyrimidinone.

[0029] A manner in which the distillation assistant is caused to bepresent is not particularly limited as long as it is a manner in whichthe distillation assistant can wash out low-temperature sublimablematerials sublimed and adhered to the inside of the distillation devicesor prevent adherence of the low-temperature sublimable materials to theinside of the distillation devices before the target organic compoundstarts to boil. For example, the distillation assistant may be mixedwith the compound to be purified in advance prior to start ofdistillation or fed directly into a distiller, a distillation column, adistilling tube or a reflux line after start of distillation.

[0030] In addition to the above effect of washing out thelow-temperature sublimable materials, effects of the distillationassistant include, for example, an effect of facilitating handling ofthe compound to be purified by decreasing the viscosity of the compoundto be purified or changing the compound to be purified into a solutionor suspension when the organic compound is solid at room temperature,through addition of the distillation assistant. Further, an effect ofachieving such purification by distillation that can be carried outefficiently without deposition of solids during distillation operation(particularly during cooling of a distillate) can also be expected. Whenthese effects are expected in addition to the above wash-out effect, aliquid having a boiling point close to the boiling point of the organiccompound is suitably added to the compound to be purified as a seconddistillation assistant.

[0031] The distillation assistant is added in an amount sufficient towash out all the low-temperature sublimable materials from thedistillation devices. The amount of the distillation assistant can bedetermined in consideration of amounts of the impurities and theirsolubilities in the distillation assistant and is preferably 0. 1 to 100parts by weight, more preferably 0.2 to 20 parts by weight, based on 1part by weight of the low-temperature sublimable materials contained inthe compound to be purified.

[0032] In the production method of the present invention, a manner inwhich the distillation is carried out in the presence of thedistillation assistant is not particularly limited, and simpledistillation or fractional distillation is used. In the case of thefractional distillation, as a fractionating column, a thin-filmfractionating column such as a vigoureux-type fractional column, aconcentric fractional column, a spinning band fractional column and apacked fractional column or a plate fractionating column such as abubble-cap fractionating column and a porous plate-type fractionatingcolumn is suitably used. When vacuum distillation is performed, athin-film fractionating column which undergoes little pressure loss isparticularly suitably used. Further, a known distillation mode such as aKugel roll or thin-film distillation can be used without anylimitations. In addition, distillation conditions including temperature,pressure and a reflux ratio are not particularly limited and may bedetermined as appropriate according to composition of the compound to bepurified, the type and amount of the distillation assistant, purity ofthe organic compound to be obtained at the end, and the like.

EXAMPLES

[0033] Hereinafter, the present invention will be described in moredetail with reference to Examples and Comparative Examples. The presentinvention, however, shall not be limited by these Examples in any way.

Example 1

[0034] To 1 part by weight of 2-methyl-2-adamantyl methacrylate with apurity of 72 wt % (boiling point: 92° C./0.3 mmHg) which contained, assublimable impurities, 2.1 wt % of adamantane (sublimation startingtemperature: room temperature or lower), 5.3 wt % of2-methyleneadamantane (sublimation starting temperature: 30° C.), 4.5 wt% of 2-adamantanone (sublimation starting temperature: 50° C.) and 1.2wt % of 2-methyl-2-adamantanol (sublimation starting temperature: 60°C.), 0.05 parts by weight of 1,3-dimethyl-2-imidazolidinone (boilingpoint: 225° C.) was added, and distillation was carried out under areduced pressure.

[0035] The distillation was carried out at a degree of vacuum of 0.3mmHg by use of a 5-cm vigoureux fractionating column and awhole-condensation-type reflux fractionating device while air was beingsupplied by means of a glass capillary. Although small amounts ofadamantane and the like which were contained as impurities wereinitially adhered inside the distillation devices, they graduallydissolved and come off after 1,3-dimethyl-2-imidazolidinone had startedto be distilled out. The impurities did not cause a blockage. A firstdistillate was removed, and a main distillate started to be collected ata point where 2-methyl-2-adamantyl methacrylate started to be distilledout. The 2-methyl-2-adamantyl methacrylate did not mix with the1,3-dimethyl-2-imidazolidinone. From the collected main distillate,2-methyl-2-adamantyl methacrylate with a purity of 97.7 wt % could beobtained.

Example 2

[0036] Distillation was carried out in accordance with Example 1 exceptthat 0.3 parts by weight of N-methylpyrrolidinone (boiling point: 81°C./10 mmHg) was used in place of 1,3-dimethyl-2-imidazolidinone used asa distillation assistant in Example 1. Sublimable impurities which hadbeen initially adhered to the insides of distillation devices graduallydissolved and come off after N-methylpyrrolidinone had started to bedistilled out. The impurities did not cause a blockage. In a maindistillate, the N-methylpyrrolidinone was mixed with2-methyl-2-adamantyl methacrylate which was distilled out. However, whenthe distillate was rinsed with pure water, 2-methyl-2-adamantylmethacrylate with a purity of 95.8 wt % could be obtained.

Example 3

[0037] To 1 part by weight of 2-ethyl-2-adamantyl methacrylate with apurity of 82 wt % (boiling point: 96° C./0.2 mmHg) which contained, assublimable impurities, 6.3 wt % of adamantane, 2.1 wt % of2-adamantanone and 0.9 wt % of 2-ethyl-2-adamantanol (sublimationstarting temperature: 60° C.), 0.1 parts by weight of tetraethylurea(boiling point: 214° C.) and 0.1 parts by weight of1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone (boiling point: 232°C.) were added, and distillation was carried out under a reducedpressure.

[0038] The reduced-pressure distillation was carried out at a degree ofvacuum of 0.2 mmHg by use of a 5-cm vigoureux fractionating column and awhole-condensation-type reflux fractionating device while air was beingsupplied by means of a glass capillary.

[0039] As a result, the distillation proceeded without any solidsprecipitated in the distillation devices. After a main distillate wasdissolved in hexane and rinsed with pure water, the hexane was removedby distillation. Thereby, 2-ethyl-2-adamantyl methacrylate with a purityof 96.5 wt % could be obtained. When the 2-ethyl-2-adamantylmethacrylate was left to stand at room temperature, it became crystals.

Example 4

[0040] To 1 part by weight of 2-butyl-2-adamantyl methacrylate with apurity of 79 wt % (boiling point: 103° C./0.2 mmHg) which contained, assublimable impurities, 5.1 wt % of adamantane, 1.1 wt % of2-adamantanone and 0.4 wt % of 2-butyl-2-adamantanol (sublimationstarting temperature: 70° C.), 0.1 parts by weight of1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone (boiling point: 232°C.) was added, and distillation was carried out under a reduced pressurein the same manner as in Example 3.

[0041] As a result, the distillation proceeded without any solidsprecipitated in distillation devices. After a main distillate wasdissolved in hexane and rinsed with pure water, the hexane was removedby distillation. Thereby, 2-butyl-2-adamantyl methacrylate with a purityof 97.5 wt % could be obtained.

Example 5

[0042] To 1 part by weight of 2-methyl-2-adamantyl methacrylate with apurity of 78 wt % (boiling point: 92° C./O. 3 mmHg) which contained, assublimable impurities, 0.05 wt % of adamantane (sublimation startingtemperature: room temperature or lower), 2.5 wt % of 2-adamantanone(sublimation starting temperature: 50° C.) and 3.8 wt % of2-methyl-2-adamantanol (sublimation starting temperature: 60° C.), 0.1parts by weight of diethylene glycol (boiling point: 245° C.) was added,and distillation was carried out under a reduced pressure.

[0043] The reduced-pressure distillation was carried out at a degree ofvacuum of 0.3 mmHg by use of a 5-cm vigoureux fractionating column and awhole-condensation-type reflux fractionating device while air was beingsupplied by means of a glass capillary. Although 2-adamantanone and2-methyl-2-adamantanol contained as impurities were initially adhered tointernal walls of the distillation devices by subliming, they graduallydissolved and come off after diethylene glycol had started to bedistilled out. The impurities did not cause a blockage. A firstdistillate was removed, and then a main distillate started to becollected at a point where 2-methyl-2-adamantyl methacrylate started tobe distilled out. The diethylene glycol did not mix with the2-methyl-2-adamantyl methacrylate and formed a separate layer under the2-methyl-2-adamantyl methacrylate. By separating the underlying layerfrom the solution, 2-methyl-2-adamantyl methacrylate with a purity of97.6 wt % could be obtained.

Example 6

[0044] Distillation was carried out in accordance with Example 5 exceptthat N-methylpyrrolidinone (boiling point: 81° C./10 mmHg) was used inplace of diethylene glycol used as a distillation assistant in Example5. Sublimable impurities which had been initially adhered to the insidesof distillation devices gradually dissolved and come off afterN-methylpyrrolidinone had started to be distilled out. The impuritiesdid not cause a blockage.

[0045] In a main distillate, the N-methylpyrrolidinone was mixed with2-methyl-2-adamantyl methacrylate which was distilled out. However, whenthe distillate was rinsed with pure water, 2-methyl-2-adamantylmethacrylate with a purity of 97.0 wt % could be obtained.

Example 7

[0046] To 1 part by weight of 2-ethyl-2-adamantyl methacrylate with apurity of 86 wt % (boiling point: 96° C./0.2 mmHg) which contained, assublimable impurities, 0.2 wt % of adamantane, 2.0 wt % of2-adamantanone and 0.8 wt % of 2-ethyl-2-adamantanol (sublimationstarting temperature: 60° C.), 0.1 parts by weight of diethylene glycol(boiling point: 245° C.) and 0.1 parts by weight of tetraethylene glycol(boiling point: 314° C.) were added, and distillation was carried outunder a reduced pressure.

[0047] The reduced-pressure distillation was carried out at a degree ofvacuum of 0.2 mmHg by use of a 5-cm vigoureux fractionating column and awhole-condensation-type reflux fractionating device while air was beingsupplied by means of a glass capillary.

[0048] As a result, the distillation proceeded without any solidsprecipitated in the distillation devices. After a main distillate wasdissolved in hexane and rinsed with pure water, the hexane was removedby distillation. Thereby, 2-ethyl-2-adamantyl methacrylate with a purityof 96.3 wt % could be obtained. When the 2-ethyl-2-adamantylmethacrylate was left to stand at room temperature, it became crystals.

Example 8

[0049] To 1 part by weight of 2-butyl-2-adamantyl methacrylate with apurity of 85 wt % (boiling point: 103° C./0.2 mmHg) which contained, assublimable impurities, 0.1 wt % of adamantane, 1.0 wt % of2-adamantanone and 0.5 wt % of 2-butyl-2-adamantanol (sublimationstarting temperature: 70° C.), 0.1 parts by weight of tetraethyleneglycol (boiling point: 314° C.) was added, and distillation was carriedout under a reduced pressure in the same manner as in Example 7.

[0050] As a result, the distillation proceeded without any solidsprecipitated in distillation devices. After a main distillate wasdissolved in hexane and rinsed with pure water, the hexane was removedby distillation. Thereby, 2-butyl-2-adamantyl methacrylate with a purityof 97.5 wt % could be obtained.

Example 9

[0051] To 1 part by weight of 2-methyl-2-adamantyl methacrylate with apurity of 65 wt % (boiling point: 92° C./0.3 mmHg) which contained, assublimable impurities, 0.1 wt % of adamantane (sublimation startingtemperature: room temperature or lower), 12.4 wt % of2-methyleneadamantane (sublimation starting temperature: 40° C.), 6.3 wt% of 2-adamantanone (sublimation starting temperature: 50° C.) and 2.7wt % of 2-methyl-2-adamantanol (sublimation starting temperature: 60°C.), 0.1 parts by weight of 1,3-dimethyl-2-imidazolidinone (boilingpoint: 225° C.) was added, and distillation was carried out under areduced pressure.

[0052] The distillation was carried out at a degree of vacuum of 0.3mmHg by use of a 5-cm vigoureux fractionating column and awhole-condensation-type reflux fractionating device while air was beingsupplied by means of a glass capillary. Although some portions ofadamantane and the like which were contained as impurities wereinitially adhered to walls of the distillation devices by sublimation,they gradually dissolved and come off after1,3-dimethyl-2-imidazolidinone had started to be distilled out. Theimpurities did not cause a blockage. A first distillate was removed, anda main distillate started to be collected at a point where purity of2-methyl-2-adamantyl methacrylate exceeded 80%. From the collected maindistillate, 2-methyl-2-adamantyl methacrylate with a purity of 97.7 wt %could be obtained.

Examples 10 to 19

[0053] Distillations were conducted in accordance with Example 9 exceptthat various distillation assistants shown in Table 1 were used in placeof 1,3-dimethyl-2-imidazolidinone used as a distillation assistant inExample 9. When a main distillate contained a distillation assistant,the main distillate was dissolved in hexane and then rinsed with purewater and then the hexane was removed by distillation so as to obtain atarget product.

[0054] The results are also shown in Table 1. Even if a large amount oflow-temperature sublimable materials were contained, adhesion of thelow-temperature sublimable materials could be inhibited effectively whena compound containing a carbonyl group was used as a distillationassistant. Distillation Assistant Purity of Target Amount Added Productin Main Ex. No. Type (Parts by Weight) Distillate (wt %) 101,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone 0.1 98.1 (boilingpoint: 232° C.) 11 1-methyl-2-piperidone (boiling point: 225° C.) 0.198.2 12 2-piperidone (boiling point: 256° C. 0.1 98.0 131,3-dimethyl-2-imidazolidone (boiling point: 225° C.) 0.05 97.41-acetylpiperidine (boiling point: 224° C.) 0.05 14 1-formylpiperidine(boiling point: 220° C.) 0.1 95.5 15 isopropyl phenyl ketone (boilingpoint: 226° C.) 0.1 95.3 16 N,N-diethylacetacetamide (boiling point:110° C./10 mmHg) 0.1 94.2 17 diethylene glycol diacetate (boiling point:245° C.) 0.1 95.7 18 diethylene glycol (boiling point: 245° C.) 0.1 91.319 dihexyl ether (boiling point: 226° C.) 0.1 89.7

Comparative Example 1

[0055] When reduced-pressure distillation was carried out without addinganything to 2-methyl-2-adamantyl methacrylate with a purity of 79 wt %which was used in Example 1, cooling pipes of distillation devices wereblocked by sublimable solids, thereby inhibiting the distillation.

Comparative Example 2

[0056] When reduced-pressure distillation was carried out without addinganything to 2-methyl-2-adamantyl methacrylate with a purity of 65 wt %which was used in Example 9, cooling pipes of distillation devices wereblocked by sublimable solids, thereby inhibiting the distillation.

[0057] As described above, according to the production method of thepresent invention, sublimable materials which sublime and adhere topipes and the like at an initial stage of distillation can be dissolvedor come off upon sublimation of the sublimable materials or by adistillation assistant which is distilled out after the sublimablematerials, thereby preventing the sublimable materials from blocking thepipes and/or dissolving in an organic compound. Further, even if adistillation assistant is mixed into an organic compound, it can beremoved easily, thereby making it possible to distill and purify anorganic compound efficiently.

[0058] According to the present invention, a high boiling compound whichhas heretofore been difficult to distill and purify, i.e., a highboiling compound containing sublimable materials as impurities, can bedistilled and purified easily. In addition, by use of the productionmethod of the present invention, a high purity alkyladamantyl esterwhich is considered promising as a resist material for a semiconductorcan be obtained easily.

1. (Amended) A method for producing a high purity alkyladamantyl esterby distilling a crude alkyladamantyl ester represented by the followingformula (1):

(wherein R³ is a hydrogen atom or an alkyl group having 1 to 6 carbonatoms and R⁴ is a hydrogen atom or a methyl group), which contains, asimpurities, sublimable materials which sublime at temperatures lowerthan a boiling point of an alkyladamantyl ester, comprising the steps ofdistilling out a compound having a boiling point lower than that of analkyladamantyl ester by carrying out the distillation in the presence ofthe compound having a boiling point lower than that of an alkyladamantylester so as to cause the compound to rinse out sublimable materialssublimed and adhered to the inside of a distillation device or preventsublimable materials from adhering to the inside of the distillationdevice and then distilling out and recovering an alkyladamantyl ester.2. (Cancelled)
 3. (Cancelled)
 4. (Amended) The method of claim 1,wherein the sublimable materials are compounds having sublimationstarting temperatures lower than the boiling point of an alkyladamantylester by 100 to 10° C.
 5. The method of claim 1, wherein the sublimablematerials are adamantane, adamantanone and alkyladamantanol. 6.(Amended) The method of claim 1, wherein the compound having a boilingpoint lower than that of an alkyladamantyl ester is an ether,polyalkylene glycol, sulfoxide, sulfolane, phosphoric acid amide,non-cyclic or cyclic ketone, aldehyde, ester, non-cyclic or cyclicamide, non-cyclic or cyclic urea, imide, acid anhydride, urethane orlactide.
 7. (Added) The method of claim 1, wherein the compound having aboiling point lower than that of an alkyladamantyl ester iswater-soluble, acid solution-soluble or basic solution-soluble compound.8. (Amended) The method of claim 1, wherein the compound having aboiling point lower than that of an alkyladamantyl ester is a cyclicurea or cyclic amide represented by the following formula (2):

(wherein R¹ is a hydrogen atom or an alkyl group having 1 to 6 carbonatoms, A is —CH₂— or >N—R² (R² is a hydrogen atom or an alkyl grouphaving 1 to 6 carbon atoms), and n is an integer of 1 to 6). 9.(Amended) The method of claim 1, wherein the compound having a boilingpoint lower than that of an alkyladamantyl ester is present in an amountof 0.1 to 100 parts by weight per part by weight of the sublimablematerials.